The present invention relates to a two-lens group type zoom lens which is composed of a first divergent lens group and a second convergent lens group and in which the first lens group is moved back and forth along the optical axis for focusing and both lens groups are moved along the optical axis for zooming. More particularly, the invention relates to a zoom lens having a macrophotographing mechanism including a focusing operational portion and a zooming operational portion.
Recently, there have been proposed a variety of so-called macro zoom lenses, that is, close focusing zoom lenses in which close-up photographing beyond the normal focusing range is possible. Such zoom lenses have already been in extensive use.
The above mentioned photographing mechanisms are applicable to a two-lens group type zoom lens. For example, there is a known mechanism in which macrophotographing is conducted by advancing the second lens group from a regular wide angle position. However, in lenses of this type, the magnification factor tends to be rather low even for telephoto operation. Additionally, with this mechanism, to move to the macrophotographing position, the lens must first be returned to the wide angle position before the change-over to the macrophotographing position can be accomplished. Therefore, the operationability of the lens is less than desired since the object seen through the viewfinder of an SLR camera first appears small and thereafter is reduced during change-over so that uniform, continuous and convenient operation of the lens is impossible.
Another mechanism is known in which the entire lens system is advanced to change to the macrophotographing position. In this mechanism, a movement mechanism or an interlock mechanism used in normal photographing to prevent accidental advance of the lens system is required. Accordingly, the mechanism is intricate in construction.
In order to overcome the above noted drawbacks inherent in the prior art mechanisms, a primary object of the present invention is to provide a macrophotographing mechanism providing a high magnification factor yet having a simple structure which has a uniform, continuous mode of operation.